The Tarforge in Marrow Keep is where you strengthen weapons, sidearms, and Tarstones in Mortal Shell 2, but almost none of it works when you first arrive. Franz, the smith who tends the machine, needs specific key items before each function switches on. The game never marks where those items are, so you can walk past the whole upgrade system for hours without realizing it exists.
Quick answer: Bring the Muradean Actuator, Obsidian Lathe, Etching Needles, and Foundry Stone to Franz to unlock weapon, sidearm, Tarstone, and smelting functions, then install the Endless Core inside the Tarforge menu to raise the upgrade cap. You can also kill Franz to unlock all four main functions instantly.
Every Tarforge item and what it unlocks
There are four main functions plus one cap-lifting extra. Four items go to Franz. The fifth, the Endless Core, is installed directly through the Tarforge’s own menu rather than handed over.
| Item | Unlocks | Where it is |
|---|---|---|
| Muradean Actuator | Enhance Weapons | Village Outskirts beacon cleanse dungeon (prologue) |
| Obsidian Lathe | Enhance Sidearms | Martyr’s Tomb, southeast of Widow’s Overlook |
| Etching Needles | Temper Tarstones | Glutted Mire, before the Magdalena fight |
| Foundry Stone | Smelt Equipment (refund upgrades) | South of the Outskirts of Mammon beacon |
| Endless Core | Raises upgrade cap to +20 | Hidden Knave beacon dungeon, near the end |
The fastest route: kill Franz
If you would rather skip the scavenger hunt, you can attack and kill Franz in Marrow Keep. Doing so unlocks all four main functions at once, so Enhance Weapons, Enhance Sidearms, Temper Tarstones, and Smelt Equipment all become available immediately, even at the very start of a playthrough. Testing shows no downside to doing this.
There is a bonus for players who go this route. Because the functions are already open, the four key items no longer trigger unlocks. Hand them in anyway and the Tarforge converts each one into crafting materials, giving you +7 Ventrium, +4 Laterite, and +3 Dorsalite per item. So collecting them is still worth it after Franz is gone.
Muradean Actuator: unlocks weapon upgrades
The Muradean Actuator is the earliest item and turns on the Enhance Weapons function for your melee gear. It sits in the Village Outskirts beacon’s cleanse dungeon, back in the tutorial area before Marrow Keep. Cleansing that beacon is mandatory to leave the tutorial, but the chest holding the item is optional, so it is technically possible to miss it.
As you enter the beacon and head toward the elevator that drops into the dungeon proper, look ahead for a chest in that first room. The Actuator is inside.
If you left the tutorial without grabbing it, you can still return. Collect at least 7 Ova from cleanse beacon dungeons in the main world, then use the Gloom Siphon in Marrow Keep to unlock Mether’s Breath. That grants fast travel between beacons and makes Village Outskirts reachable again.
Obsidian Lathe: unlocks sidearm upgrades
The Obsidian Lathe enables Enhance Sidearms and lives in the Martyr’s Tomb dungeon in Fainweald. From the Widow’s Overlook beacon, turn southeast, pass the arena where you fight the Great Arbiter of Flesh world boss, and head for the large church-like building. The tomb entrance is just inside.
In the final room you will find a chest beside a sarcophagus, guarded by priest enemies. The Lathe is inside, alongside the Parasitic Stone Tarstone. Note that the exit seals once you enter that room. To reopen it, aim your sidearm and shoot the target above the metal door.
Etching Needles: unlocks Tarstone tempering
The Etching Needles switch on Temper Tarstones, which lets you level up the passive-effect stones you slot into weapons. They are in the Glutted Mire, the Corrupted Gate area next to the Mushroom Village Gate beacon on the eastern side of the map.
Push through the level until you defeat the Tarblighted Shepherd, the boss that summons sheep, then squeeze through the fence behind the arena. Keep going along the wooden bridges until you reach Ruk, perched on an arch, warning you about Magdalena. The chest holding the Needles is right underneath him, and it is unguarded, so you can grab it and return to Marrow Keep quickly.
Foundry Stone: unlocks smelting
The Foundry Stone turns on Smelt Equipment, which reverts a weapon to its unleveled state and refunds the materials you spent on it. Start from the Outskirts of Mammon beacon, which is already unlocked from the beginning of the game.
Look south and you will spot a slope down to a battlefield packed with regular and elite soldiers. You do not need to kill them. Run straight through toward the wall fortifications, find the chest next to the wall surrounded by soldiers, and interact with it to claim the Stone.
Endless Core: raises the upgrade cap
The Endless Core removes the standard upgrade ceiling and lets weapons and sidearms reach +20. It only appears near the very end of the campaign, so expect major story spoilers to reach it.
Complete all Corrupted Gates and gather enough Ova to trigger the final ending. After a run of boss fights leading into the confrontation with Zmei, the dragon, you unlock the Hidden Knave beacon just before that final battle. Cleanse the beacon, and the Endless Core waits in a chest inside its cleanse dungeon. Unlike the other four items, you install it through an option in the Tarforge menu rather than handing it to Franz.
How to confirm each function is active
Head to the Tarforge in Marrow Keep after handing items to Franz. From the beacon, move toward the Gloom Siphon room and take the left path up to the machine. A function is unlocked once its option appears in the Tarforge menu, so you should see Enhance Weapons, Enhance Sidearms, Temper Tarstones, and Smelt Equipment fill in as you deliver each item. If an option is still greyed out or missing, the matching item has not been delivered yet.
Upgrading itself costs Coins plus smithing stones such as Ventrium, Laterite, Dorsalite, Thoracium, and Ossinite. Tarstones work differently. They gain XP only while slotted in an equipped weapon or sidearm as you kill enemies, and once a stone hits its XP threshold you level it at the Tarforge, spending Coins and earning Tarcore that higher tiers then consume. Keep those two currencies stocked and every Tarforge function stays ready whenever you return to Marrow Keep.
